Process for making multi-color intaglio plates and cylinders for use in gravure printing

ABSTRACT

In a photogravure process for making sets of intaglio plates for use in multi-color gravure printing a special type of halftone screen is used in a special manner. Said screens are characterized by closely spaced parallel lines of connected dots extending in a single direction as distinguished from crossed lines of discrete dots as in halftone screens used in offset lithography, and from the crossed solid lines of the screens commonly used in photogravure processes. A set of such screens is assembled with a set of continuous tone color separated positive transparencies with the lines of connected dots of each screen arranged at an angle to the horizontal which is different from the angle to the horizontal at which the corresponding lines of connected dots of each other screen are arranged. The said assemblies are then exposed separately onto photosensitive material and the latent images are transferred onto a copper plate in conventional manner and the plates are then etched in conventional manner.

United States Patent [191 Bergin PROCESS FOR MAKING MULTI-COLOR INTAGLIOPLATES AND CYLINDERS FOR [52] US. Cl. 96/38; 96/45; 96/116 [51] Int. Cl.G03F 5/00; G03F 7/24 [58] Field of 96/38, [16, 45

[56] References Cited UNITED STATES PATENTS 6/1902 Szczepanik 96/452/1935 Grenell 96/116 2,480,400 8/ 1949 Dultgen 2,700,609 l/l955Landom...

3.024,l ll 3/l962 Sportelli.....

3,804,622 4/1974 Bergin 96/38 OTHER PUBLICATIONS Photo Mechanics andPrinting, Mertle et al., 1957, pp. 144-145.

[ Dec. 23, 1975 Primary Examiner-Mary F. Kelley Attorney, Agent, orFirm-Nichol M. Sandoe [57] ABSTRACT ln a photogravure process for makingsets of intaglio plates for use in muIti-color gravure printing aspecial type of halftone screen is used in a special manner. Saidscreens are characterized by closely spaced parallel lines of connecteddots extending in a single direction as distinguished from crossed linesof discrete dots as in halftone screens used in offset lithography, andfrom the crossed solid lines of the screens commonly used inphotogravure processes, A set of such screens is assembled with a set.of continuous tone color separated positive transparencies with thelines of connected dots of each screen arranged at an angle to thehorizontal which is different from the angle to the horizontal at whichthe corresponding lines of connected dots of each other screen arearranged. The said assemblies are then exposed separately ontophotosensitive material and the latent images are transferred onto acopper plate in conventional manner and the plates are then etched inconventional manner.

8 Claims, 5 Drawing Figures PROCESS FOR MAKING MULTI-COLOR INTAGLIOPLATES AND CYLINDERS FOR USE IN GRAVURE PRINTING This invention relatesto photogravure processes and pertains more particularly to processes ofmaking sets of intaglio plates including both flat plates and cylindersfor use in multicolor gravure printing. It will be understood that theterm plates as used hereinafter includes both flat plates and cylinders.

It is an object of the invention to improve the quality of the intagliosurfaces formed in such plates by the use of a special type of halftonescreen used in a special manner, whereby an improved lay of ink isobtained which results in smoother printing and helps to eliminatephenomena known in the trade as skipping and picking" which result inunevenesss and white specks in the printing. The quality of the printsmade from such plates is improved.

Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention is shown in the accompanyingdrawings, in which FIG. 1 is a greatly enlarged plan view of a smallsection of a halftone screen as used in the process of the inventionFIGS. 2, 3, 4 and 5 are diagrammatic representations of a set ofhalftone screens illustrating the angles at which the lines of connecteddots of the respective screens are arranged for use with a set of fourcolor separated continuous tone positive transparencies corresponding tofour different colors.

The practice of the invention depends importantly on the use, in a novelmanner, of a special type of halftone screen which is characterized byclosely spaced parallel lines of connected dots, as distinguished fromcrossed lines of discrete dots as in the usual halftone screens commonlyused in offset lithography, and as distinguished from the crossed solidlines of the screens com monly used in photogravure processes.

Such a halftone screen is illustrated in greatly enlarged scale in FIG.I in which all of the dots 1 of each of the lines of dots are connectedtogether, in the manner of a chain of dots, by narrow necks 2 of a widthconsiderably less than the maximum width of the dots. Moreover, as shownin FIG. I, all of the lines of connected dots are parallel and extend ina single direction. The opposed dots of adjacent lines of dots are notconnected. The maximum width of the dots is preferably less than thedistance between opposed dots of adjacent lines. In the use of suchscreens in this process, the said lines of dots are commonly arranged100 to 250 lines per inch.

In the use of such screens in the making of sets of color separatedintaglio plates for use in multi-color gravure printing, the lines ofconnected dots of each screen are arranged at a predetermined angle tothe horizontal, i.e., to a transverse line which extends in a directionperpendicular to the direction of movement of the paper on which theimage is printed as it moves through the press. as indicated by thetransverse horizontal lines 3. The direction of movement of the paper isindicated by arrows 4. In the following description of the invention,the predetermined angles of the lines of connected dots are related tothe horizontal as above defined.

Moreover, in the use of such screens in the making of sets of colorseparated intaglio plates for use in multicolor gravure printing, thepredetermined angle at which the lines of connected dots of each screenare arranged with respect to the horizontal is different from that ofeach other screen. That is, in the case of four color process printing,for example, in which four separate screens as shown in FIGS. 2, 3, 4and 5 are used in connection with yellow, red, blue and black colorseparations, respectively, the angle at which the lines of connecteddots of each screen are arranged with respect to the horizontal will bedifferent for each color as hereinafter explained.

The invention may be best understood with reference to a specificexample of its use in a four color process, and for clarity andcompleteness, the entire process leading to the making of a set of fourfinished intaglio plates will be described, although it will beunderstood that many of the steps described are conventional in the art.The principal novelty of the invention resides in the use of screens asabove described in the particular manner described in Steps 3 and 4hereinafter.

STEP 1. The first step in the process is the photographing anddeveloping by conventional processes of a set of four color separatedcontinuous tone negative transparencies corresponding to four differentspecific primary colors as, for example, yellow, red, blue and black,preferably color corrected and retouched if necessary.

STEP 2. A set of four continuous tone developed positive transparenciesis now made from said four negative transparencies by conventionalprocesses, as by contact printing.

STEP 3. A set of four positive halftone screens of the type shown inFIG. 1 and heretofore described is now prepared, each of said screensbeing of equal value, i.e., the lines of connected dots of therespective screens are identical except as to their angulation, and thenumber of lines per inch is identical. The lines of connected dots ofeach screen are arranged at a specific angle with respect to theparticular continuous tone positive with which it is to be assembled,which said angle is different from the specific angle at which the linesof connected dots of each other screen are arranged with respect to theparticular continuous tone positive with which it is to be assembled. Ingeneral, the predetermined angles of the lines of connected dots to thehorizontal should all exceed 45 in order to avoid doctor blade chatterand spillout of ink. Thus, in the case of screens intended for assemblywith yellow, red, blue and black continuous tone positives as previouslydescribed and as shown in FIGS. 2, 3, 4 and 5, the lines of connecteddots 5 of the screen of FIG. 2 which is to be assembled with the yellowpositive should be arranged at an angle of (:3) to the horizontal aspreviously defined; the lines of connected dots 6 of the screen of FIG.3 which is to be assembled with the red positive should be arranged atan angle of 49 (13) to the horizontal; the lines of connected dots 7 ofthe screen of FIG. 4 which is to be assembled with the blue positiveshould be arranged to an angle of (t3) to the horizontal; and the linesof connected clots 8 of the screen which is to be assembled with theblack positive should be arranged at an angle of I07 (:3") to thehorizontal.

STEP 4. Each of the four continuous tone positives is now assembled incontact with its respective related screen on a line carrier plate knownand sometimes referred to in the trade as a cabriolet. That is, the yel-3 low positive film is assembled with a screen such as shown in FIG. 2in which the lines of connected dots are at an angle of 75 to thehorizontal; the red film is assembled with a screen such as shown inFIG. 3 in which the lines of connected dots are at an angle of 49thereto and so on.

STEP 5. Each of the above assemblies is now exposed separately ontophotosensitive resist material, such as carbon tissue, to form a latentimage thereon, and the photosensitive material is then transferred andadhered to a copper plate.

STEP 6. The plates may now be etched in the conventional manner to formintaglio images therein. However, for best results, it is preferred toetch each plate with three irons of progressively decreasing baume for atotal period of eight minutes at 69.5F. with the total periods dividedas follows:

If desired, the method of producing halftone positive films describedand claimed in my co-pending patent application Ser. No. 315,030, filedDec. 4, 1972 may be combined with the present process in order to avoidjagged edges along the marginal edges of the images which may be causedby the varying angulations of the respective halftone screens.

What is claimed is:

l. A process of making a set of color separated intaglio plates for usein multi-color gravure printing which comprises the steps of making aset of continuous tone color separated positive transparencies, each ofwhich bears a color separated image corresponding to a specific colordifferent from the specific color of each other image, and assemblingeach of said transparericies separately with a transparent halftonescreen having closely spaced parallel lines of connected opaque dotsextending in a single direction, said dots being ofa length greater thantheir width and with successive dots connected by narrow necks of awidth substantially less than the maximum width of the dots with saidlines of connected dots of each of said screens arranged at an angle tothe horizontal which is different from the angle to the horizontal atwhich the corresponding lines of connected dots of each other screen arearranged.

2. A process according to claim I in which the maximum width of saiddots is less than the distance between opposed dots of adjacent lines.

3. A process according to claim 1 in which all of said lines ofconnected dots are arranged at angles to the horizontal which exceed 45.

4. A process according to claim 1 in which said set of continuous tonepositive transparencies includes one bearing a yellow image. one bearinga red image, one bearing a blue image and one bearing a black image, andin which the lines of connected dots of the screen assembled with thetransparency bearing the yellow image are arranged at an angle of (:3")to the horizontal, the lines of connected dots of the screen assembledwith the transparency bearing the red image are arranged at an angle of49 ("i-3) to the horizontal, the lines of connected dots of the screenassembled with the transparency bearing the blue image are ar' ranged atan angle of (:3") to the horizontal, and the lines of connected dots ofthe screen assembled with the transparency bearing the black image arearranged at an angle of 107 (t3) to the horizontal.

5. A process according to claim 1 which includes the step of exposingeach of the said assemblies onto photosensitive material to form alatent image thereon, transferring each of said latent images onto aseparate copper plate, and etching each of the said plates separately toform an intaglio image therein.

6. A photogravure process for making a set of color separated intaglioplates for use in multieolor gravure printing in which a set ofcontinuous tone color separated positive transparencies, each of whichbears a color separated image corresponding to a specific colordifferent from the specific color of each other image is assembled witha set of halftone screens, and in which each assembly is exposedseparately onto photosensitive material to form a latent image therein,in which the improvement comprises assembling each of said continuoustone color separated positive transparen cies separately with atransparent halftone screen having closely spaced lines of connecteddots, said dots being of a length greater than their width and withsuccessive dots connected by narrow necks of a width substantially lessthan the maximum width of the dots with each screen arranged at an angleto the horizontal which is different from the angle to the horizontal atwhich the corresponding lines of connected dots of each other screen arearranged.

7. A process according to claim 6 in which the maximum width of saiddots is less than the distance between opposed dots of adjacent lines.

8. A process according to claim 6 in which all of said lines ofconnected dots are arranged at angles to the horizontal which exceed 45.

1. A PROCESS OF MAKING A SET OF COLOR SEPARATED INTAGLIO PLATES FOR USEIN MULTI-COLOR GRAVURE PRINTING WHICH COMPRISES THE STEPS OF MAKING ASET OF CONTINUOUS TONE COLOR SEPARATED POSITIVE TRANSPARENCIES EACH OFWHICH BEARS A COLOR SEPARATED IMAGE CORRESPONDING TO A SPECIFIC COLORDIFFERENT FROM THE SPECIFIC COLOR OF EACH OTHER IMAGE, AND ASSEMBLINGEACH OF SAID TRANSPARENCIES SEPARATELY WITH A TRANSPARENT HALFTONESCREEN HAING CLOSELY SPACED PARALLEL LINES OF CONNECTED OPAQUE DOTSEXTENDING IN A SINGLE DIRECTION, SAID DOTS BEING OF A LENGTH GREATERTHAN THEIR WIDTH AND WITH SUCCESSIVE DOTS CONNECTED BY NARROW NECKS OF AWIDTH SUBSTANTIALLY LESS THAN
 2. A process according to claim 1 in whichthe maximum width of said dots is less than the distance between opposeddots of adjacent lines.
 3. A process according to claim 1 in which allof said lines of connected dots are arranged at angles to the horizontalwhich exceed 45*.
 4. A process according to claim 1 in which said set ofcontinuous tone positive transparencies includes one bearing a yellowimage, one bearing a red image, one bearing a blue image and one bearinga black image, and in which the lines of connected dots of the screenassembled with the transparency bearing the yellow image are arranged atan angle of 75* ( + or -3*) to the horizontal, the lines of connecteddots of the screen assembled with the transparency bearing the red imageare arranged at an angle of 49* ( + or - 3*) tO the horizontal, thelines of connected dots of the screen assembled with the transparencybearing the blue image are arranged at an angle of 90* ( + or - 3*) tothe horizontal, and the lines of connected dots of the screen assembledwith the transparency bearing the black image are arranged at an angleof 107* ( + or - 3*) to the horizontal.
 5. A process according to claim1 which includes the step of exposing each of the said assemblies ontophotosensitive material to form a latent image thereon, transferringeach of said latent images onto a separate copper plate, and etchingeach of the said plates separately to form an intaglio image therein. 6.A photogravure process for making a set of color separated intaglioplates for use in multi-color gravure printing in which a set ofcontinuous tone color separated positive transparencies, each of whichbears a color separated image corresponding to a specific colordifferent from the specific color of each other image is assembled witha set of halftone screens, and in which each assembly is exposedseparately onto photosensitive material to form a latent image therein,in which the improvement comprises assembling each of said continuoustone color separated positive transparencies separately with atransparent halftone screen having closely spaced lines of connecteddots, said dots being of a length greater than their width and withsuccessive dots connected by narrow necks of a width substantially lessthan the maximum width of the dots with each screen arranged at an angleto the horizontal which is different from the angle to the horizontal atwhich the corresponding lines of connected dots of each other screen arearranged.
 7. A process according to claim 6 in which the maximum widthof said dots is less than the distance between opposed dots of adjacentlines.
 8. A process according to claim 6 in which all of said lines ofconnected dots are arranged at angles to the horizontal which exceed45*.